Williams syndrome is a genetic disorder producing mental retardation, characteristic dysmorphology, and cardiac defects. In most cases it results from a hemizygous deletion around the elastin gene on chromosome 7q11.2. The present study is designed to examine the cognitive sequellae of Williams syndrome and to determine the genetic basis for the cognitive defects. Genotype-phenotype correlations are being performed by collecting detailed clinical information on patients studied at the Salk Institute for Biological Studies and obtaining blood from them for molecular studies. Lymphoblastoid cell lines are being establishment by the GCRC at Cedars-Sinai, ensuring that adequate quantities of DNA will be available for the detailed molecular evaluations of 7q11.2. Patient accrual will continue in the coming year.